1) Field of the Invention
The present invention relates to a scroll type compressor which can be used, for example, in an air-conditioning system of a vehicle such as an automobile, and more particularly, to a scroll type compressor provided with an improved lubricating arrangement for movable parts thereof.
2) Description of the Related Art
For example, Japanese Unexamined Patent Publication No. 57-62988 discloses a scroll type compressor for an air-conditioning system of an automobile, which comprises immovable and movable scroll members housed in a housing and having spiral guide walls engaged with each other in such a manner that spaces are formed as a compression chamber therebetween. The movable scroll member is revolved around a center axis of the immovable scroll member in such a manner that an engagement is maintained between the spiral guide walls of the immovable and movable scroll member, and that the spaces or compression chambers therebetween are displaced toward centers of the spiral guide walls.
During the revolution of the movable scroll member around the center axis of the immovable scroll member, a compression chamber appears successively at the outsidemost portions of the spiral guide walls thereof, and opens to take in a refrigerant, including a lubricating oil mist, fed from an evaporator of the air-conditioning system, and then the compression chamber concerned is fully closed by the spiral guide walls, due to the revolution of the movable scroll member. Thereafter, as the compression chamber concerned is displaced toward the centers of the spiral guide walls, a volume thereof becomes gradually smaller, whereby the refrigerant confined therein is compressed, and when the compression chamber concerned reaches the centers of the spiral guide walls, the compressed refrigerant is discharged through a reed valve into a discharge chamber formed in the housing of the compressor. After the discharge of the compressed refrigerant into the discharge chamber is completed, the compression chamber concerned disappears at the centers of the spiral guide walls, and thus a compression of the refrigerant is successively carried out.
To cause the revolution of the movable scroll member around the central axis of the immovable scroll member, the compressor comprises a drive shaft projected from the housing and operatively connected to and rotated by a prime mover of the vehicle, and an eccentric mechanism provided between the drive shaft and the movable scroll member for converting the rotation of the drive shaft into the revolution of the movable scroll member. The drive shaft is provided with a seal assembly to prevent a leakage of the refrigerant from the housing, and is rotatably supported by a radial bearing. The eccentric mechanism includes an eccentric pin element projected from an enlarged portion of the drive shaft, and a bush element rotatably engaged with the eccentric pin element and rotatably received in a sleeve portion projected from the movable scroll member through the intermediary of a radial bearing. The drive shaft, the bush element and the sleeve portion are axially aligned with each other, and thus the movable scroll member can be revolved around the central axis of the immovable scroll member by the rotation of the drive shaft.
Also, to constrain the movement of the movable scroll member, to thereby ensure the revolution thereof around the central axis of the immovable scroll member, the compressor comprises a first annular plate fixedly disposed at a rear side of the movable scroll member and having a plurality of circular recesses formed therein, and a second annular plate attached to a rear side wall surface of the movable scroll member and facing the first annular plate, and having the same number of circular recesses formed therein. The circular recesses of the first and second annular plates are radially disposed so that each of the circular recesses of the first annular plate partially overlaps the corresponding circular recess of the second annular plate, and two shoe elements are slidably received in each pair of the partially overlapped circular recesses of the first and second annular plates in such a manner that a ball element is slidably disposed between and held by the two shoe elements. With this arrangement, the movement of the movable scroll member is constrained, and thus the revolution thereof around the central axis of the immovable scroll member is ensured.
The various movable parts of the compressor as mentioned above are exposed to the refrigerant fed from an evaporator of the air-conditioning system, and thus are lubricated with lubricating oil separated from refrigerant. When an excessive amount of the oil mist is included in the refrigerant, although the movable parts are sufficiently lubricated, the larger the amount of oil mist, the lower the cooling efficiency of the air-conditioning system, and accordingly, in the conventional compressor, the compressed refrigerant discharged from the compression chamber into the discharge chamber through the reed valve is directed to and impinged on an inner wall surface of the discharge chamber, so that a part of the oil mist is separated from the refrigerant, and the separated oil is stored in the discharge chamber. Nevertheless, an amount of the separated oil obtained depends upon the running conditions of the compressor, such as a rotational speed of the drive shaft and a rate of flow of the compressed and discharged refrigerant, etc., and thus an amount of the oil mist included in the refrigerant cannot be maintained at a constant value during the running of the compressor. Accordingly, when an amount of the oil mist is too small, the movable parts are not sufficiently lubricated and may seize up. Conversely, when the amount of the oil mist is too large, the cooling efficiency of the air-conditioning system is lowered, as mentioned above.